1. Field of the Invention
The present invention relates to a high frequency surgical instrument to be used in combination with an endoscope, for performing a high frequency surgical operation at a high frequency current.
2. Description of the Related Art
The diathermic snare is a generally known example of the high frequency surgical instrument, which is inserted into a body cavity, for example, through a channel of an endoscope to perform a high frequency surgical operation on living tissue in the body cavity by allowing a high frequency current to flow in the instrument. The diathermic snare includes a snare loop made by folding a wire over into a loop shape and a plastic sheath. The snare loop is pierced through the plastic sheath such that it can be put into it and out. Then, living tissue in the body cavity is put into the snare loop and the loop is narrowed down while keeping the tissue within the loop, thereby tightening the living tissue. Then, a high frequency current is allowed to flow through the snare loop, and thus the fastened living tissue is cut.
The handle portion of the diathermic snare is made of a main body thereof and a slider. To the main body of the handle portion, a proximal end of the plastic sheath is mounted. The slider can move forward and backward on the main body. An operation wire is connected by its distal end to the snare loop, and the proximal end of the operation wire is connected to the slider. As the slider is moved forward and backward by manipulation, the snare loop can be put in and out of the plastic sheath by means of the operation wire.
Meanwhile, Jpn. U.M. Appln. KOKAI Publication No. 55-173307 (Patent Document 1) and U.S. Pat. No. 4,256,113 (Patent Document 2) disclose another structure of the diathermic snare. According to this structure, a connector is provided for the slider. A connection cord for an external high frequency current supply device is connected to the connector. With this structure, a high frequency current is supplied to the snare loop.
Jpn. Pat. Appln. KOKAI Publication No. 2000-197643 (Patent Document 3) and U.S. Pat. No. 5,769,880 (Patent Document 4) disclose another structure in which a finger placing portion in which the operator put a finger, is provided in the slider. Patent Document 3 discloses a structure in which the connector is provided to project vertically to the axial direction of the slider. Meanwhile, the device of Patent Document 4 has a structure in which the connector is provided to project at an angle with respect to the axial direction of the slider.
U.S. Pat. No. 5,066,295 (Patent Document 5) discloses a diathermic snare that includes a knob for rotating the snare loop at this handle portion. The slider has a connector. This document describes a structure in which as the knob is rotated with respect to the slider, the direction of the snare loop is changed to a desired direction by rotating the snare loop.
Further, Jpn. U.M. Application KOKOKU Publication No. 61-18885 (Patent Document 6) discloses a structure in which the snare loop is rotated by turning the entire handle portion.